As an Intermap partner Murphy Surveys can provide digital elevation data from the Intermap NEXTMap and World 30 databases to support GIS, planning and infrastructure design applications.
The NEXTMap database elevation data is available in the form of Digital Surface Models (DSM) and Digital Terrain Models (DTM) at a resolution of 5m. Also available are Orthorectified Radar Images (ORI) at a resolution of 1.25m, these images are similar to grayscale aerial photography.
Digital Surface Model & Digital Terrain Model
The DSM is a first-reflective-surface model that contains elevations of natural terrain features in addition to vegetation and cultural features such as buildings.
The DTM is a bare-earth model that contains elevations of natural terrain features such as barren ridge tops and river valleys. Elevations of vegetation and cultural features, such as buildings and roads, are digitally removed from the dataset.
Both digital elevation models are seamless, wide-area, and current terrain data allowing you to perform more accurate cross-border geospatial analyses in applications. The NEXTMap DSMs and DTMs are available in two versions.
• Hydro-enforced digital surface model – structures over water bodies (such as bridges) are removed, water surfaces are flat, and watercourses flow downstream – making them ideal for water resource and floodplain management applications.
• Ortho-ready digital surface model – bridge decks are maintained in the elevation models, and major roads are smooth to accommodate the use of the surface models in orthorectification of optical images.
Orthorectified Radar Image
The ORI is produced from NEXTMaps proprietary interferometric synthetic aperture radar (IFSAR) sensors and provides an image in regions where there is persistent cloud cover. The orthorectified radar image is a grayscale radar image of the earth’s surface that has been corrected to remove geometric distortions caused by terrain.
The orthorectified radar image accentuates topographic features such as rivers, road networks, and vegetation boundaries. Many geospatial applications can be supported by the orthorectified radar image, including topographic and geological mapping, land coverage classification, and forestry analyses.
Geographical Information Systems (GIS)
Over the past decade Geographical Information Systems (GIS) have changed from highly specialised applications used in specific areas of research, to more common server and desktop applications that are now employed by businesses of all types and sizes. GIS has even impacted at a consumer level through such applications as Google Earth and OpenStreetMaps.